Mary Barra rose to the top of General Motors after 33 years at the company.

Barra started at the very bottom of General Motors at age 18, when she enrolled in an engineering college sponsored by the company. There, she spent half the year inspecting parts at a Pontiac plant, according to Fortune.

She worked her way up the ladder with smart decision-making and a willingness to give the company everything she had. The Financial Times reports colleagues recall her being the first person in the office every morning and responding to emails after 11 p.m.

In 2013, her dedication was rewarded when she was named GM's first ever female CEO.

Dallas Mavericks owner Mark Cuban didn't take a vacation for seven years while starting his first business.

At first glance, Cuban's amazing success looks like a stroke of luck. He sold his first company at the peak of its value and got into technology stocks at exactly the right time.

Cuban writes on his blog that it took an incredible amount of work to benefit from his luck. When starting his first company, he routinely stayed up until 2 a.m. reading about new software, and went seven years without a vacation.

Petrobras chief Maria Das Gracas Silva Foster's work ethic earned her the nickname "Caveirao," slang for the armored vehicles used by police in Brazil.

The current head of Brazilian Oil Giant Petrobras spent her childhood in a favela collecting cans to pay for school. She started as an intern in 1978, but quickly became the company's first female head of field engineering.

Bloomberg reports that her tireless work ethic has earned her the nickname Caveirao, for the armored vehicles police use to clean up crime-ridden Brazilian neighborhoods.

Amazon CEO Jeff Bezos' high school classmates gave up when he decided he wanted to be valedictorian.

Bezos always had a relentless work ethic. A former classmate told Wired that once Bezos made it clear that he intended to be high school valedictorian, "everyone else understood they were working for second place."

The early days at Amazon were characterized by working 12-hour days, seven days a week, and being up until 3 a.m. to get books shipped.

Nissan and Renault CEO Carlos Ghosn flies more than 150,000 miles a year.

Carlos Ghosn runs two of the world's largest automakers, which should tell you something about his work ethic. A profile in Forbes describes how Ghosn works more than 65 hours a week, spends 48 hours a month in the air, and flies more than 150,000 miles a year.

His turnaround of Nissan is the subject of many case studies. Within a month of taking over in 1999, he deployed a system that completely changed ingrained practices, helping save a company many thought irredeemable.

Hong Kong business magnate Li Ka-Shing became a factory general manager by age 19.

One of the richest men in Asia and a dominant figure in Hong Kong's economy, Ka-Shing started outworking everybody as a teenager en route to building a $31 billion empire.

By age 15, Ka-Shing had left school and was working in a plastics factory. He told Forbes how he quickly became a salesman, outsold everybody else, and became the factory's general manager by 19. In 1950, he started his own plastics business and did almost everything, including the accounting, himself.

Facebook COO Sheryl Sandberg balances one of the most varied and busiest lives of anybody in business.

Any one of the things Sandberg does would be impressive and take an incredible amount of work on their own. In all, she's the highly successful and influential COO of a multi-billion dollar company, a massively successful author, and one of the most recognizable advocates in the world for women in the workplace.

Jordan had prodigious physical gifts. But as his long-time coach Phil Jackson writes, it was hard work that made him a legend. When Jordan first entered the league, his jump shot wasn't good enough. He spent his off seasons taking hundreds of jumpers a day until it was perfect.

In a piece at NBA.com, Jackson writes that Jordan's defining characteristic wasn't his talent, but having the humility to know he had to work constantly to be the best.

WPP CEO Sir Martin Sorrell is a legendary workaholic whose employees can expect emails at any hour of the night.

A former client described sending Sir Martin a message while he was in a different time zone in the earliest hours of the morning. Sir Martin responded almost immediately.

Yahoo CEO Marissa Mayer routinely pulled all nighters and worked 130-hour weeks while at Google.

Mayer is known for her incredible stamina and work schedule. She used to put in 130-hour weeks at Google, according to Entrepreneur, a schedule she managed by sleeping under her desk.

Even people critical of her management style acknowledge that she "will literally work 24 hours a day, seven days a week," Business Insider's Nich Carlson reports. That paid off with one of the biggest jobs in technology.

GE CEO Jeffrey Immelt spent 24 years putting in 100-hour weeks.

A 2005 Fortune article on Immelt describes him as "The Bionic Manager." The article highlights his incredible work ethic, saying he worked 100-hour weeks for 24 years. Immelt strictly divides that time, devoting a specific portion of each day to deal with every part of his business.

All of that comes after a 5:30 a.m. workout, during which he's already reading the papers and watching CNBC.

Lakers superstar Kobe Bryant completely changed his shooting technique rather than stop playing after breaking a finger.

Nobody in basketball drives their body harder than Bryant. A profile in GQ describes how he has changed his shooting technique repeatedly rather than take time for dislocated and broken fingers.

When growing up outside of Philadelphia, ESPN describes how Kobe would spend his free time endlessly practicing jump shots in the park. The Lakers staff finds him doing the same thing at their practice facility at all hours of the day and night.

Pepsi CEO Indra Nooyi worked the graveyard shift as a receptionist while putting herself through Yale.

Now one of the most powerful and well-known women in business, Nooyi worked midnight to 5 a.m. as a receptionist to earn money while getting her masters degree at Yale.

Today, she wakes up at about 4 a.m., according to Fortune. At the Aspen Ideas Festival earlier this year, Nooyi said that at times during her career it has been normal for her to work until midnight. During that same talk, she said her intense dedication to her job may have made her a worse parent.

Elon Musk tells other entrepreneurs they need to work twice as hard as everyone else.

"You just have to put in 80- to 100-hour weeks every week," he tells Vator. "If other people are putting in 40-hour work weeks and you're putting in 100-hour work weeks, then, even if you're doing the same thing, you know that you will achieve in four months what it takes them a year to achieve."

This ability to keep pushing was on display in August 2008 after SpaceX's third unsuccessful attempt to launch a rocket into space. Musk put out a statement telling the world, "For my part, I will never give up and I mean never."